The present invention relates to encryption. More specifically, the present invention relates to a novel method and apparatus of encryption using binarization and phase information of encrypted data in terms of display or transmission of encrypted data.
Image data security has recently become an important issue. An image is generally a two-dimensional data. In accordance with which, a one-dimensional signal or two-dimensional image may need encryption in many applications for security reasons. Also, encryption of memory, which may comprise one or more images, can be considered. Furthermore, optical security and encryption methods using random phase encoding have been proposed recently, see generally xe2x80x9cOptical pattern recognition for validation and security verificationxe2x80x9d, by B. Javidi and J. L. Homer, Opt. Eng. 33, 1752-1756 (1994). Also see, xe2x80x9cExperimental demonstration of the random phase encoding technique for image encryption and security verificationxe2x80x9d, by B. Javidi, G. Zhang and J. Li, Optical Engineering, 35, 2506-2512, 1996; xe2x80x9cFault tolerance properties of a double phase encoding encryption techniquexe2x80x9d, by B. Javidi, A. Sergent, G. Zhang, and L. Guibert, Optical Engineering, 36(4), 992-998, 1997; xe2x80x9cPractical image encryption scheme by real-valued dataxe2x80x9d, by Yang, H.-G., and E.-S. Kim, Optical Engineering, 35(9), 2473-2478, 1996; xe2x80x9cRandom phase encoding for optical security, by Wang, R. K., I. A. Watson, and C. Chatwinxe2x80x9d, Optical Engineering, 35(9), 2464-2469, 1996; xe2x80x9cOptical implementation of image encryption using random phase encodingxe2x80x9d, by Neto, L. G. Y. Sheng, Optical Engineering, 35(9), 2459-2463, 1996; and xe2x80x9cOptical image encryption using input and Fourier plane random phase encodingxe2x80x9d by Ph. Refregier and B. Javidi, Optics Letters, Vol. 20, 767-770, 1995.
The above-discussed and other drawbacks and deficiencies of the prior art are overcome or alleviated by the method and apparatus of encrypting optical images using binarization and phase information. An image to be encrypted is first multiplied by a key, e.g., a random phase function. The Fourier transform of the product of the image and the random phase function is then multiplied by another key, e.g., another random phase function in the Fourier domain. Taking the inverse Fourier transform, an encrypted image in the output plane is obtained. In accordance with the present invention, this encrypted image is then binarized, which may include binarizing the phase-only part of the encrypted image. The use of binarization enables ease of implementation and data compression while still providing recovery of images having good quality. In addition, the phase of the encrypted image only can be use for description, which makes it easier to display the encryption using techniques such as embossing.
The above-discussed and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description and drawings.